The operating environment within a gas turbine is both thermally and chemically hostile. For example, operating temperatures within a gas turbine may range from about 1200° F. to about 2200° F. (about 650° C. to about 1200° C.), depending on the type of turbine engine being used. Such high temperatures combined with the oxidizing environment of a gas turbine generally necessitates the use of a nickel- or cobalt-containing specialty alloy having a high oxidation resistance and, thereby, an acceptable operating life within the turbine. Accordingly, gas turbine components are typically formed from nickel alloy steels, nickel-based or cobalt-based superalloys or other specialty alloys.
Significant advances in the high temperature capabilities of such specialty alloys have been achieved through the use of oxidation resistant environmental coatings capable of protecting the alloys from oxidation, hot corrosion, etc. For example, thermal barrier coating (TBC) systems are typically used in turbine components to insulate the components from the high temperatures during thermal cycling. TBC systems typically include a thermal barrier coating disposed on a bond coating which is, in turn, applied to the metal substrate forming the component. The thermal barrier coating normally comprises a ceramic material, such as zirconia. Additionally, the bond coating typically comprises an oxidation-resistant metallic layer designed to inhibit oxidation of the underlying substrate.
Current trends show that less refined fuels are gaining in popularity for use within gas turbines. These less refined fuels include particulate matter that can make its way into the hot gas path of the gas turbine, thereby impinging on the turbine components contained within the hot has path. The continued exposure of turbine components to such particulate matter can lead to erosion damage of the coatings within the TBC system, thereby increasing the likelihood that the underlying metal substrate is subject to oxidation and/or hot corrosion. To address such erosion issues, erosion resistant bond coatings have been developed. However, these erosion resistant bond coatings are typically formed by increasing the size and volume percent of the hard particles (e.g., tungsten carbide, titanium carbide and diamond boron nitride) used in the coating. As a result, the volume percent of the oxide-forming constituents within the coating must be decreased, thereby reducing the overall environmental protectiveness of the coating.
Accordingly, a method for forming an oxide-dispersion strengthened coating that provides erosion resistance without sacrificing environmental protectiveness would be welcomed in the technology.